The present invention relates to a light-controlling device used for controlling illumination of an indicator or an operating panel in a vehicle.
A conventional light-controlling device illuminates an indicator or an operating panel using an incandescent lamp or a light emitting diode (LED). Operating a variable resistor changes an electric output of a controlling circuit, so that illumination of the incandescent lamp or the LED is controlled.
The conventional light-controlling device is described hereinafter with reference to FIGS. 8-10. FIG. 8 shows a circuit diagram of a conventional light-controlling device used for a vehicle. FIG. 9 shows an outward appearance of a dashboard in a vehicle. As shown in FIGS. 8 and 9, connecting terminal 1 of a power supply e.g., battery, is coupled with incandescent lamp 2 for illuminating indicator 3 and the like. Connecting terminal 1 is also coupled with diode 6 for suppressing surge. In addition, diode 6, fixed resistance 7 for controlling an electric current, and light emitting diode (LED) 4 for illuminating meter 5 such as a speed meter or a fuel meter are connected in series.
Controlling circuit 8, which generates voltage waveforms, is coupled with variable resistor 9 which is operated by rotating. Transistor 10 for controlling an electric current is coupled with controlling circuit 8, incandescent lamp 2 and LED 4.
FIG. 10 is a graph showing a characteristic of a resistance for an operating angle. A resistance value rate for an operating angle varies linearly as shown in characteristic R1 of FIG. 10.
When operating section 11 of variable resistor 9 rotates, an operating angle changes, thereby changing a resistance value rate. Then an output voltage from controlling circuit 8 changes, and an electric current through transistor 10 is controlled. As a result, illumination of incandescent lamp 2 and LED 4 change, and brightness of indicator 3 and meter 5 on a dashboard change.
However, when incandescent lamp 2 differs from LED 4 in characteristic, a minimum voltage of illuminating lamp 2 differs from that of LED 4 at predetermined illumination. In that case, when operating section 11 rotates for turning off, indicator 3 illuminated by lamp 2 and meter 5 illuminated by LED 4 are not turned off simultaneously. As a result, an operator feels strange.
The present invention aims to provide a light-controlling device, which is used for a vehicle and includes the following elements:
(a) a controlling circuit coupled with a plurality of light-emitting sections, which have minimum voltages different from each other at predetermined illumination,
(b) a variable resistor for changing illumination of the plurality of light-emitting sections by changing an electric output of the controlling circuit,
where when the illumination of the plurality of light-emitting sections decreases to the predetermined illumination using the variable resistor, the controlling circuit turns the plurality of light-emitting sections off simultaneously based on a signal from a detecting section which is linked with the variable resistor.